Prognostic impact of interim positron emission tomography in mantle cell lymphoma patients treated with frontline R-CHOP

Although ¹⁸F-fluorodeoxyglucose positron emission tomography (¹⁸F-FDG PET) is commonly used for initial staging and therapeutic response evaluation in aggressive lymphomas, its prognostic utility for mantle cell lymphoma (MCL) is controversial. Therefore, we retrospectively evaluated the correlations of interim PET (iPET) and end-of-treatment PET (ePET) response with survival outcomes in 89 consecutive advanced MCL patients treated with frontline R-CHOP (rituximab, cyclophosphamide, doxorubicin, vincristine and prednisolone). iPET positivity was strongly associated with inferior five-year overall survival (OS) hazard ratio (HR) 7·84, P < 0·0001] and poor five-year progression-free survival (PFS) (HR 3·34, P < 0·0001). OS and PFS were more favourable in the order early metabolic responder (iPET^neg → ePET^neg), delayed responder (iPET^pos → ePET^neg), loss-metabolic responder (iPET^neg → ePET^pos), and never-metabolic responder (iPET^pos → ePET^pos). In the autologous haematopoietic stem cell transplantation (auto-HSCT)-fit subgroup, OS was more favourable in the order early metabolic responders, delayed metabolic responders, and non-metabolic responders, with a marginal trend toward statistical significance (HR 3·41, P = 0·051), and PFS was significantly superior in early metabolic responders (HR 4·43, P = 0·002). In a group that was ineligible for auto-HSCT, OS and PFS were significantly superior in early metabolic responders. Our results suggested that iPET is of prognostic value and an independent predictor of survival in MCL patients receiving frontline R-CHOP. Therefore, prospective clinical trials of iPET-guided treatment strategies for these patients are warranted.